The present invention relates to the field of inflatable structures. More particularly, the present invention relates to sequential controlled gas generation in a plurality of respective cells of a cellular inflatable structure for preferred potential use during inflation of inflatable structures on orbiting spacecraft.
Presently, conventional space systems utilize a number of different mechanical schemes for deploying antennas, solar arrays and payload sensors, which reside on an orbiting spacecraft. One such system deploys rigid honeycomb panels in the case of solar arrays or masts with antenna elements attached in the case of antennas. Particularly for solar panels, a power sphere deployment scheme has been patented teaching the use of sublimation powders contained in frame cells of an inflatable structure. These microsatellites and nanosatellites have an overall small surface area. The deployable power sphere is made of external solar panels configured in an approximate sphere shape for providing an attitude insensitive high solar collection area with low weight and with low stowage volume. The power sphere deployment method required an inflatable deployment sequence that moves the individual flat panels from the stacked stowage configuration to an unfolded deployed configuration where the individual panels form the spherical solar array structure upon completion of the deployment sequence. Ideally, the deployment of primary, secondary, and tertiary polygon panels of the power sphere is sequential and controlled. Inflatable frames around each of the polygonal panels are inflated sequentially so that the stacked set of polygons complete deploying movement in a controlled sequence from the stacked stowed configuration to the deployed configuration. Sublimation powders in the frame cells provide sufficient gas pressure to unfurl the stack during the deployment sequence as the sublimation powder expands into a gaseous state when the panels are released in turn as the power sphere is deployed. This deployment scheme is based upon sequential releases, and not sequential control, of the panels, where the sequence is based on the sequential stacking order of the panels with the use of expanding sublimation powders in each of the frames. The use of sublimation powder does not provide for direct sequential control of the inflation process, but rather relies solely on the sequence of stacking of the panels into the stacked stowage configuration prior to launch.
To accomplish electronically controlled sequential deployment of a cellular inflatable structure, a conventional inflation system requires a complicated set of control valves, one or more gas canisters, and necessary gas tubing to supply the gas in controlled sequence. The gas tubing runs from a gas canister to all of the individual cells of the inflatable structure. Gas tubing disadvantageously extends through the walls of the cellular structure increasing failure rates where the tubing penetrates the walls, which can fail with high leakage rates. The use of mechanical valves and gas canisters adds significant weight to the inflatable structure and reduces the overall reliability of the deployment system. Hence, conventional gas canister deployment systems disadvantageously have significant structural weaknesses and large mass requirements. With the advent of thin film solar cells and the use of thin film devices, the mass of a conventional deployment system may be disadvantageously many times greater than the deployed apparatus, such as a deployed solar array or deployed antenna. To reduce overall weight and provide sequential inflation control, there exists a need for new designs using new lightweight materials for deploying inflatable structures of a spacecraft after launch.
Presently, microelectromechanical systems (MEMS) devices are being developed. MEMS processing techniques are preferred in a space application where mass allowance budgets are critical requirements. These MEMS devices include thrusters and pressure transducers, fabricated on silicon chips, using microelectronics manufacturing techniques. Other MEMS devices include addressable arrays for fuel cells for providing sequentially controlled combustion thrust. However, MEMS devices that would otherwise provide inflation gas would still require extensive intercellular gas tubing and gas release control valves for controlled deployment, but having undesirable excessive weight and inherently low reliability. These and other disadvantages are solved or reduced using the invention.
An object of the invention is to provide a method of sequentially controlling the inflation of a cellular inflatable structure.
Another object of the invention is to provide a method of sequentially controlling the inflation of a cellular inflatable structure having gas generators inside respective cells of the cellular inflatable structure.
Yet another object of the invention is to provide a system for sequentially controlling the inflation of a cellular inflatable structure having evaporation gas generators inside respective cells of the cellular inflatable structure.
Still another object of the invention is to provide a system for sequentially controlling the inflation of a cellular inflatable structure having ablation gas generators inside respective cells of the cellular inflatable structure.
The present invention is directed to a generalized method and specific system means for sequentially controlled inflation of inflation cells in a cellular inflatable structure having only electronic control and power lines integrated into the walls of each cell. A gas MEMS device capable of generating an inflation gas is disposed in each of the cells and used for controlled sequential deployment of the inflation cells of the space inflatable structure. The MEMS device could enable small increments of gas release so that the amount of gas in each cell and the inflation sequence is electronically controlled.
The gas MEMS device contains all of the associated electronics for controlling the release of gas to the inflatable structure and determining the resultant pressure change in the inflatable structure. The control electronics is capable of executing a preprogrammed inflation sequence and of communicating status along with any measured parameters, to a central spacecraft processor unit. The MEMS devices preferably operate using DC current and control lines supplied from a spacecraft bus. In a general aspect of the invention, a method is used to inflate the cellular inflatable structure where a gas MEMS device is disposed in each cell with the MEMS devices being sequentially controlled to sequentially inflate the inflatable structure. In a first aspect of the invention, evaporation gas MEMS devices are disposed in respective cells of the cellular inflation structure for sequential controlled inflation. In a second preferred aspect of the invention, ablation gas MEMS devices are disposed in respective cells of the cellular inflation structure for sequential controlled inflation of the of the cell. These and other advantages will become more apparent from the following detailed description of the preferred embodiment.